Right Plant. Right Process. Right Place.Restore Our Blue Flag. Protect Liscannor Bay.

Right Plant

Fit for purpose now and in the future.

Fit for purpose, now and in the future. A new plant will serve Lahinch and Ennistymon for decades. It must be sized for real year-round and peak summer demand, perform reliably, and be able to meet tighter standards as they come in.

What “population equivalent” means

Wastewater plants are sized in “population equivalent” (PE). One PE is the organic load produced by one person in a day, set in EU law as 60 grams of BOD5 per day. PE is not the same as the number of residents: it also covers visitors, hotels, businesses and other sources. In a resort town like Lahinch, summer load is much higher than winter load.

Sources: Council Directive 91/271/EEC (Urban Waste Water Treatment Directive), Article 2(6).

The figures in the public record

Different documents give different capacity figures. We think the public is entitled to a clear explanation of how each was arrived at.

FigureWhat it refers toSource
8,400 PEDesign capacity of the Lahinch plant: “designed to treat a population equivalent (p.e.) of 8,400”. Relied on by An Bord Pleanála in March 2023.EPA licence D0080-01, 7 October 2010, page 4; An Bord Pleanála Inspector’s Report ABP-314268-22, 30 March 2023, section 7.2.2
2,100 PECapacity of the Ennistymon plant.EPA licence D0081-01; Ennistymon 2024 AER
3,500 PELahinch capacity first put to the EPA by Uisce Éireann in an email of 11 April 2024, then used in the revised Lahinch 2024 Annual Environmental Report.EPA AIE release ORM AIE 2026 18, Record 06; revised Lahinch 2024 AER, approved 19 November 2025
9,330 PEDesign load for the proposed combined plant in 2055 (Lahinch 6,502 PE plus Ennistymon 2,828 PE), described publicly as about 9,300 PE.Uisce Éireann pre-planning presentations, 2024 to 2026 (FOIR2198)
10,000 PEThreshold in Irish planning law above which an Environmental Impact Assessment is mandatory for a wastewater plant, and an EU threshold for treatment standards for discharges to coastal waters.Planning and Development Regulations 2001, Schedule 5, Part 2, Class 11(c); Directive 91/271/EEC

Uisce Éireann has stated, in response to a request under environmental information law, that it has identified no record showing how the 3,500 PE figure was derived and “No formal decision record changing the stated design capacity from 8,400 PE to 3,500 PE”. On the long-standing licence figures, the two existing plants were rated at 10,500 PE together (Lahinch 8,400 PE and Ennistymon 2,100 PE). The single plant proposed to replace them is designed at 9,330 PE. We have asked for the working papers.

Sources: Uisce Éireann AIE decision AIER449, 6 October 2026, page 2; EPA licences D0080-01 and D0081-01.

Our questions

  1. How was each capacity figure calculated, by whom and when? Will the working papers be published?
  2. Does the design allow for peak summer visitor numbers, planned housing and business growth in both towns?
  3. How will the plant perform in storms and flooding, and how often is it expected to overflow?
  4. What are the energy use, operating costs and maintenance needs over the life of the plant?
  5. Can the plant be upgraded to meet the revised EU Urban Wastewater Treatment Directive (EU) 2024/3019 without major rebuilding?
  6. Has upgrading or extending the existing infrastructure been compared on an equal footing with a new combined plant?

What we are asking for

A plant sized on transparent, published figures, with room for growth, and an evidence-based comparison with upgrading existing infrastructure.